Identical twins have exactly the same DNA, but they are not exactly alike. Each twin has his or her own personality, talents, likes, and dislikes. There are even diseases that appear in one twin but not the other, including arthritis, diabetes, autism, schizophrenia, cancer, and many others. The differences between identical twins don’t come from DNA—they all come from external factors.

Scientists often study twins to understand how genes and the environment work together to affect traits. They compare traits in identical twins, who have identical DNA, and fraternal twins, who share half their DNA, just like any siblings. If a characteristic appears more frequently in identical twin pairs than in fraternal twin pairs, then it has an inherited component.

CR:https://learn.genetics.utah.edu/content/basics/trait/

5 heredity examples

1.Dimple

A dimple (also known as a gelasin)[1] is a small natural indentation in the flesh on a part of the human body, most notably in the cheek or on the chin.

Tongue rolling is the ability to roll the lateral edges of the tongue upwards into a tube. The tongue’s intrinsic muscles allow some people to form their tongues into specific shapes. Popular belief holds that variation in this ability is the result of genetic inheritance. Rolling the tongue into a tube shape is often described as a dominant trait with simple Mendelian inheritance, and it is commonly referenced in introductory and is genetic biology courses.[1]

There is little laboratory evidence supporting the hypothesis that tongue rolling is inheritable and dominant. In 1940, Alfred Sturtevant observed that ~70% of people of European ancestry could roll their tongues and the remaining ~30% could not do it.[2] A 1975 twin study found that identical twins were no more likely than fraternal twins to both have the same phenotype for tongue rolling.[3]

Cloverleaf tongue is the ability to fold the tongue in a certain configuration with multiple bends. To the extent to which it is genetic, it is probably a dominant trait distinct from tongue rolling.[3]